1. Field of the Invention
The present invention generally relates to management of a production line including a plurality of process units, and in particular to a method for deciding an inspection schedule of the process units.
2. Description of the Related Art
A production line having a plurality of process units arranged in series must be periodically checked for proper and stable operation. Since a process unit must stop operating in order to be checked, it is very important to decide upon an inspection schedule of the process units so that an output of the production line is not decreased by a large amount.
Conventionally, a simulation technique is used to decide such upon an on schedule. More specifically, a model of the production line is created by adding many constraints and then a managing operator explores the model's behavior displayed on screen, that is, a change of the number of in-process workpieces in the simulated production line. Based on the time-varying number of in-process workpieces, the managing operator decides the inspection schedule of the process units.
However, such a model is only as good as its input constraint data. If the input constraint data is not correct, the model does not accurately mimic the behavior of the real-world production line being simulated. In the case where the simulation is performed without consideration of the speed of workpieces conveyed, for example, the time-varying number of in-process workpieces substantially departs from that of the real-world production line, resulting in reduced reliability in line control.